A printing plate is a rectangular aluminum plate, typically 0.0 12 inch in thickness, carrying an image on one surface and having two opposite edges bent downwardly forming tabs that facilitate mounting the plate on a printing cylinder. The bent-down edges or tabs are inserted into a slot that extends longitudinally of the cylinder and are clamped firmly in place to hold the plate tightly against the outside surface of the printing cylinder. When the plates are being transported to the press room, it is important to protect them from any possible damage. If the bent down edges or tabs of the plates are harmed in any way during transit or are bent or pushed out of tolerance, or if the angle of the tab or the radius of the bend between the main portions of the plate and the tab is changed, a serious accident can result because of the high speed of the printing cylinder which has recently been increased to as much as 50 feet per second and has caused imperfect printing plates to fly from the cylinder with explosive force. Consequently, a precise fit is vitally important to keep the printing plates operating properly. Prior methods of transporting the plates have, however, exposed them to possible damage.
One carrier previously used for transporting printing plates included a series of trays stacked one above the other. During use, one printing plate is placed in a horizontal position on each of the trays. Each carrier can hold only eight or ten printing plates, and the pressman must reach in between the trays to insert or remove the plates. The lower plates are hard to reach since they are close to the floor. Consequently, this type of carrier has limited capacity, is cumbersome, and is awkward to use. In addition, the rigid structure of the carrier makes it unsuited for compact shipment and storage, and difficult and/or impossible to get through doorways separating one department from another. In another system, the plates are placed one on top of the other with slip sheets of paper between them to protect the image. The center of each successive plate arches further upward because the radius of the end tabs fit inside one another. This method of stacking the plates is time consuming and requires special care to make sure the plates or end tabs do not become bent or otherwise damaged. The hard metal surfaces of a carrier can also damage the printing plates.
In view of these and other shortcomings of the prior art, it is one object of the present invention to provide a printing plate carrier that is light in weight, occupies little space so that it is inexpensive to ship, but can reliably transport a substantial number of printing plates from the make-up room where the plates are produced to the press room where the plates are used with little chance that the plates will be damaged.
It is a further object of the invention to find a way to reduce the size of the space occupied by the carrier to facilitate compact shipment and storage and passage through standard doorways, but yet allows the carrier to be readily assembled for transporting a relatively large number, e.g., 32, printing plates during use.
It is a further object to provide an improved printing plate carrier which, although capable of carrying 32 plates or more, is still narrow enough so that it can pass through a standard door opening 30 inches wide.
These and other more detailed and specific objects of the present invention will be better understood by reference to the following figures and detailed description which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims.